Sealing mechanisms for storage tanks



3 Sheets-Sheet 1 Filed Feb. 23, 1960 FIG./

IN VEN TOR.

FRANK W. HORNER, JR,

BY 6M 04 2. g Z ATTYS.

July 10,1962

Filed Feb. 23, 1960 F. w. HORNER, JR 3,043,468

SEALING MECHANISMS FOR STORAGE TANKS 5 Sheets-Sheet 2 a In:

.ii 55; iii; \OIL LEVEL INVENTOR.

FRANK W. HORNER, JR.

ATTYS.

July 10, 1962 F. w. HORNER, JR

SEALING MECHANISMS FOR STORAGE TANKS 3 Sheets-Sheet 3 Filed Feb. 23, 1960 COMPRESSION FORCE, LB. /$O. IN.

INVENTOR.

FRANK W. HORNER, JR.

. J ATTYS.

United States Patent F7 eral American Transportation Corporation, Chicago,

corporation of New York Filed Feb. 23, 19,60, Ser. No. 10,431

11 Claims. (Cl. 220-26) The present invention relates to sealing mechanisms for storage tanks for petroleum products, or the like, and more particularly to such a storage tank of the type having an upstanding substantially cylindrical sidewall and provided with a floating roof carrying, the sealing mechanismwith it arranged in sliding and sealing engagement with the side Wall, thereby to minimize evaporation of the stored petroleum products from the storage tank and to protect the same from the elements of the weather.

Itis a general object of the invention to provide a sealing mechanism of thetype noted, that is of improved and simplified construction and arrangement.

Another object of the invention is to provide a sealing mechanism of the type noted, wherein constant and adequate surface contact is maintained by the sealing mechanism with the inner surface of the side wall of the tank, notwithstanding substantial irregularities in the side wall.

Another object of the invention is to provide a sealing mechanism of the .type noted, wherein the lower portion thereof is submerged at all times in the stored petroleum products, thereby preventing the formation of a vapor space above the products and below the sealing mechanism, so as to minimize the fire hazard.

Another object of the invention is to provide a sealing mechanism of the/typevv noted that is exceedingly versatile in adaptation to such a floating roof, whereby the same may be readily installed upon a new floating-roof incident to constructing a new storage tank or upon an old floating roof incident to renovating an old storage tank.

A further object of the invention is to provide a sealing mechanism of the type noted, that comprises an hermetical- 1y sealed hollow ring formed of flexible sheet-like material and of tubular configuration and arranged in the annular space disposed between the cylindrical wall structure of the floating roof and the cylindrical side wall of the storage tank, and an annular body of resilient porous material in the solid state arranged within the hollow ring and constituting a resilient cushion acting between opposed inner and outer annular portions of the hollow ring, so as to urge the inner annular portion of the hollow ring into firm engagement with the wall structure of the floating roof and to urge the outer annular portion of the hollow ring into firm engagement with the side wall of the storage tank, thereby to maintain an eflicient sliding seal between the sealing mechanism and the side wall of the storage tank, notwithstanding side-to-side movements of the floating roof with respect to the storage tank, as 'well as the usual vertical movements of the floating roof with respect to the storage tank, and substantial irregularities in the inner surface of the side wall of the storage tank.

Further features of the invention pertain to the particular arrangement of the elements of the sealingmechanism,

whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the fol-' lowing specification, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a top perspective view, partly broken away, of a tank for storing liquids, such as petroleum products, and provided with a floating roof carrying sealing mechanism embodying the present invention;

FIG. 2 is an enlarged fragmentary top perspective view of. a portion .ofthev side wall of the storage tank and an adjacent portion of the floating roof carrying the sealing mechanism'men tioned, this view being taken generally in the direction of the arrows along the line- 2 2 in FIG. 1; FIG/3 is an enlarged fragmentary-plan view of a portion of thesealing mechanism carried by the floating roof;

FIG. 4, is an enlarged vertical sectional view of the sealing mechanism, taken in the direction of the arrows along the line 4--4 in FIG. 3;

FIG. 5 is a greatly enlarged horizontal sectional view of the sealing mechanism, taken in the direction of the arrows along the line 5-5 in FIG. 4; i I

FIG. '6 is a greatly enlarged horizontal sectional view of the sealing mechanism, taken in the direction of the arrows along the line 6 6 in FIG. 4; and

FIG. 7 .is a graphic representation of certain characteristics of the annular cushioning member incorporated in the sealing mechanism. 7 a r I Referring now to FIGS. 1 and 2 of the drawings, there is illustrated a tank 19 for storing liquids, such as petroleum products, that includes an upstanding substantially j cylindrical side wall 11 and provided with an open top bounded by an annular rim 12 and carrying an annular catwalk 13 arranged about the upper outer portion thereof and disposed adjacent to and below the annular rim 12..

Also an annular roof 20 is arranged in the tank 10. in floating relation with respect to the stored liquid; whereby the floating roof 20 rises and falls withrespectto the side wall 11 of the tank 10 in accordance with the head of the body of liquid stored therein.

As best illustrated in FIGS., 1, 3 and 4, the floating root l 20 comprises inner annular structure defining a centrally. disposed annular pontoon 21, outer; annular structurev defining an outer annular pontoon 22, and connecting annular structure defining a deck 23 disposed, between the pontoons 21 and 22. As best shown in FIGS. 2, 3 and 4,, the outer annular pontoon 22 comprises upstanding substantially cylindrical wall structure 24 spaced radially in-, wardly from the tank side wall 1 1 and defining an annular space 25 therebetween; and arranged within the annular space 25 and carried by the floating roof 20 is sealing mechanism 30 embodying the features of the As indicated in FIG. 4, when the.

present invention. roof 2-0 is floating upon the body of liquid stored in the tank 10, the lower portion of the pontoon 22 is submerged therein, the normal liquid level in thetank 10 being indicated by the broken line 26.

Continuing the reference to 'FIGS. 3 and 4, the sealing mechanism 30 essentially comprises a hollow ring 31 of tubular configuration and formed of flexible sheet- I like material and arranged in the space 25 and attached to the floating roof 20 so that it is movable therewith in Y the vertical direction with respect to the tank side wall 11. As illustrated, the hollow ring 31 comprises aninner annular wall portion 3-2 disposedin fixed sealed engagement with the adjacent wall structure 24 of the pontoon22, and an outer annular wall portion 33 dis-' sections of the wall portions 32 and 33. Also the seal ing mechanism 30 comprises an annular body 40 .of resilient material in the solid state and arranged within' the hollow ring 31 and constituting a resilient cushion acting between the inner and outer annular wall portions 32 and 33 thereof, so as to urge the inner annular wall portion 32 into firm engagement with the wall structure 24 and to.urge the outer annular wall portion 33 into I Patented July,.l0, 1962- ing side-tQ-side movements and also vertical move ments, of the floating roof 2!} with respect to the tank sidewall 11. Further, the sealing mechanism .30 is retained in itsmounted position upon theadjacent wall structure 24 offthe floating roof by an arrangement including a number of upstanding circumferentially spacedapart' stays or bars 50 secured to the outer surface of the wall structure 24.

More particularly, the. extreme upper edge of the upstanding wall structure 24- carries an upstanding surrounding annular ring 26 rigidly secured thereto, as by welding; and to this annular ring 26, the sealing mechanism is detachably secured by an arrangement including another surrounding annular ring 27 and 'a series of circumferentially spaced-apart bolts 28 provided with cooperating nuts 29. In the arrangement, the extreme upper end of the inner wall portion 32 and the extreme upper end of the top wall portion of the hollow ring 31 are disposed in facing engagement with each other and positioned between the clamping rings 26 and 27 and held securely together in clamped relation therebetween, so that the hollow ring 3-1 is hermetically sealed. Also, in the; arrangement, the upstanding stay bars are arranged in clamped relation between the rings 26 and 27; and more particularly, the upper end of each of the stay bars 50 is disposedbebween the clamping ring 26 and the adjacent extreme upper edge of the inner wall portion 32 of the hollow ring 31 and clamped in position between the clamping rings 26 and 27 by the action of the bolts28 and the cooperating nuts 29 carried thereby. Specifically, in the arrangement, each of the upstanding stay'bars 50 penetrates the upper portion of the inner annular wall portion 32 just below the adjacent clamping ring 26 and also penetrates the junction between the inner annular wall portion 32 and the bottom wall portion 34; whereby the upper and lower ends of each of the stay bars 50 is disposed exterior-1y of thehollow ring 31, while the intermediate portion of each of the stay bars. 50 is, in fact, disposed within the hollow ring 31. "Furthermore, the openings in the hollow ring 3 1 through which each of the stay bars50 projects are suitably sealed so as to preserve the hermetic sealing of the hollowf'ring. 31. Also thelower end of each of; the stay bars 50 projects through a loop-like member 51 secured, as by welding, to the outside lower surface of the adjacent wall structure 24, as -illustrated in FIG. 6, the looplike mem-bcrs 51 being circurnferentially spaced-apartand poisitione dbelow the bottom wall portion 34 of the hollow 31.

Recapitulating: the upper end of each of the stay bars 50 projects through the opening provided in the upper portion of' the adjacent inner annular wall portion 32 of thehollow ring 31 and is hermetically sealed in the opening mentioned, while the lower end of each or the stay bars 50 projects through the opening provided in the lower portion of the adjacent inner annular wall portion 32of the hollowring 31 and is hermetically sealed in the opening mentioned. The extreme upper end of each of thestay bars, 50 is secured in place by the associated bolt 28 to the adjacent portion of the clamping, ring 26, and the. extreme lower end of each of the stay bars 50. is secured in place by the associated loop-like member 51.

As previously noted, the hollow ring 31 is formed of flexible sheet-like material and essentially comprises asheet of synthetic organic resinous material; and pref erably, this sheet material comprises the. synthetic rubber, composition sold commercially under the name Ensolite Type M, by the. U8. Rubber Company. Specifically, this synthetic rubber composition comprises nitrile rubber modified by polyvinyl chloride resin, the composition, containing-by, weight about 75% of the nitrile rubber; in turn, the nitrile rubber comprises copolymers of butadiene and acrylonitn'le, the butadiene content rangingfrorn about 55% to 80% by weight.

A This synthetic rubber composition is type and is of a tough cellular construction, having the general appearance of foamed rubber. Moreover, the composition is capable of vulcanization in a manner entirely similar to that of natural rubber, but shows superior resistance to oils and solvents in general, and withstands the effect of aging, abrasion and heat much better than,

natural rubber. Also, thissynthetio rubberc omposition is superior to natural rubber with respect to mininnzing swelling thereof in the presence of petroleum products.

Referring now to FIGS. 4 and 5, the annular body of 1 resilient'rnaterial 40 that is'enclosed within the hollow ring 31 essentially comprises a block of synthetic organ- Q '41 in the three rows mentioned are staggered with respect to each other, as illustrated in FIG. 5. In the arrangement, the biock 40 occupies a major fraction of the volume of the hollow ring 31, as illustrated in FIG. 4; and

specifically, the block ,40 may occupy about of the total volume of the hollow ring 31. Furthermore, the total porosity of the block 41 is about 80%; whereby the total gas space within the hollow ring 31 is about of the total volume thereof. In the arrangement,

the block 40 extends between the inner upstanding annular wall portion 32 and the outer upstanding annular wall portion 33 and serves as a resilient cushion located therebetween, the inner and outer upstanding faces of the block 40 being suitably cemented to the adjacent faces of the wall portions 32 and 33 by intervening layw ers of cement, indicated at 32a and 33a in FIG. 5; whereby the opposed inner and outer upstanding faces of the block 40 are intimately united by thecement layers 32a and 33a respectively to the adjacent surfaces of the wall portions 32 and 33 of the hollow ring 31. On theother hand, the bottom face of the block 44) is not secured to the adjacent bottom wall portion 34 of the hollow ring 31 so that the bottom wall portion 34 is free to move with respect to the bottom surfaceof the block 40'; and

likewise,-the upper face of the block 40 is spaced well 1 below the adjacent top wall portion 35 of the hollow ring 31. Accordingly, a principal gas pocket 36 is formed in the upper portion of the hollow ring 31 above the block 4-0 and directly communicating with the upper ends of the upstanding openings 41 provided through the block 413*; and moreover, the block 40 is of opencell C011". struction, as previously noted. The principal gas pocket 36, defined in the hollow ring 31, is ordinarily filled with air, which of course permeates the structure of the porous block 40, since it is of open-cell construction, asp reviously noted.

In view of the foregoing, it will be understood that as the floating roof 20 rises and falls in the tank 10, it carries therewith the sealing mechanism 30 filling the an nular space between the upstanding wall structure 24 of the pontoon 22 and the cylindricalv tank side wall 11 and maintaining a seal therebetween so as to minimize the evaporation of petroleum products from the body thereof stored in the tank 10. Moreover the stay bars 50 prevent the hollow ring 31' from rolling, upwardly with respect to the Wall structure 24 incident to downward movement of the floating roof 20 with respect to the tank side wall 11 and maintains the inner annular wall portion 32 of the hollow ring 31 firmly pressed into fixed sealed engagement with the adjacent upstanding wall structure 24 of the pontoon 22. Also the resilient block 40' maintains the outer annular wall portion 33. in

of the closed-cell I firm sliding sealed engagement with the tank side Wall spective slippages therebetween incident to the vertical movements of the floating roof 20 with respect tothe ttank side wall 11. Furthermore, the resiliency of the block 40 maintains firm compression between the op-, posed wall portions 32 and 33 of the. hollow ring 31, notwithstanding substantial side-to-side movements of the floating roof 20 with respect to the tank side wall 11 that occur particularly during substantial wind storms. Also, it will be understood that the porous character of the block 40 accommodates free pumping action of the air between the principal gas pocket 36 and the body structure thereof incident to expansion or contraction of a segment of the hollow ring 31, as a consequence of sidewise movements of the floating roof 20 with respect to the tank side wall 11. In the arrangement, the bottom wall portion 34 of, the inner ring 31 is maintained in submerged condition with respect to the liquid stored in the tank and regardless of the vertical movements and the sidewise movements of the floating roof with respect to the tank side Wall 11, thereby to prevent the formation of a gas pocket in the annular space disposed below the bottom wall 34 of the hollow ring 31 so as to minimize the fire hazard.

Further, the floating roof 20 carries a composite anhular weather hood that is movable therewith in the vertl'cal direction with respect to the tank side Wall 11; and as best illustrated in FIGS. 3 and 4, the weather hood essentially comprises a plurality of overlapped segments 60 positioned above the sealing mechanism and disposed in covering relation with respetc to the top of the annular space 25, each of the segments 60 being pitched radially outwardly and upwardly from the roof and projecting over the extreme top end of the wall structure 24 of the outer pontoon 22 with the outer circumferential edge thereof disposed in sliding engagement with the tank side wall 11 and with the inner circumferential edge thereof disposed radially inwardly with respect to the wall structure 24 and overhanging the outer circumferential portion of the deck 23. Specifically, a plurality of circumferentially spaced-apart and radially outwardly extending arms 61 are carried by the clamping ring 26 and project over the sealing mechanism 30, each arm 61 terminating at the outer end thereof in a downwardly carried loop 62 disposed adjacent to the tank side wall 11; and each of the arms 61 supports the intermediate portion of one of the weather hood segments 60. As illustrated, each of the arms 61 is provided with an upstanding lug 63 intermediate the ends thereof that projects through a cooperating slot 60a provided in the adjacent portion ofthe overlying weather hood segment 60, whereby the weather hood segments 60 are removably secured in place upon the arms 61 and in overlapping relation with respect to each other, so as to protect the annular space 25. The extreme outer end of each of the weather hood segments 60 carries a flexible wiper 64 formed of a.,suitable synthetic rubber, or the like, and that is disposed in sliding engagement with the adjacent inner surface of the tank side wall 11.

In the arrangement, the arms 61 possess resiliency so that they are capable of bending or flexing upwardly in cident to substantial sidewise movement of the floating roof 20 toward the adjacent tank side wall 11; whereby in this event, the loop 62 provided on the extreme outer end of one of the arms 61 engages the adjacent portion of the side wall 11 and rides upwardly thereon flexing the corresponding arm 61 upwardly with respect to the inner end thereof that is attached by the corresponding bolt 28 to the annular clamping ring 26. Accordingly, as the floating roof 20 moves toward the tank side wall 11 in a sidewise movement thereof, the arm 61 is flexed upwardly eflecting a corresponding upward movement of the carried sidewise movement of the floating roof 20., Thereafter,

when the floating roof 20 is -again centeredandimovedaway from the portion oftheltank side wall 11 mentioned,- the flexible arm 61 disengages theyadjacent portion of; thetank side wall 11 andreturns downwardly back into its normal position, thereby lowering thesupported weather-1 hood segment 60 back into its normal'upwardlyinclined position, as shown in FIG.' 4. v

In view of the fo'regoinggit will be understood thatthe construction and arrangement of the composite weather hood accommodates, without injury thereto, both vertical movements and side-to-side movements ofthe floating roof 20 with respect to the tank side wall 11. Also the composite weather hood protects the sealing mechanism 30 at all times agaisnt damage thereto by rain, snow, ice

and other elements of weather andregardless of various. movements of the floating roof 20 with respect to the tank installed either upon a new floating roof incident to the building thereof or upon an old floating roof incident to renovation thereof, in a simplewand ready manner; and moreover these items may be readily mounted upon a wide variety of floating roof constructions by virtue of the unitary character of the sealing mechanism 30 and of the composite weather hood.

As a constructional example of the sealingmechanism 30, the sheet material of the hollow tube 31 may have a thickness of about /2"; 'each or" the vertical stay bars 50 may have a length of about 30"; the block 40 in unstrained condition may have a radial width between the inner and outer annular wall portions 32 and 33 of the hollow ring 31 of about 15"; the outer vertical height of the block 40 adjacent to the outer ananular wall portion 33 may be about 12"; and the inner vertical height of the block 40 adjacent to the inner annular wall portion The total coring of the block- 32 may be about 18". 40 may be about 39% and the cellular structure of the material of the block 40 may have a density of about 1.6-1? per cu. ft. In this constructional example of the sealing mechanism 30, the compression characteristic of the block 40 is indicated generally by the curve 70 shown in the graph of FIG. 7. Specifically, the curve 70 com-- prises a plot of the percentage deflection of the blockAO suifers a 60% deflection or deformation at a pressure of about 14# per square inch between the wall portions-32 and 33. A portion of the composite characteristic of the block 40 is derived from the inherent resiliency of the foamed material thereof, while another factor exerting a substantial influence thereupon is the circumstance that this highly cored open-cell structure is hermetically sealed in the hollow ring 31; whereby Tthe'cornposi'te characteristic described is obtained, so that the block 40 constitutes a resilient porous cushion disposed between the inner and, outer annular wall portions 32 and 33 of the hollow ring 31, thereby retaining the elements 32 and 33 in firm engagement with the respective elements24 and 11 and preventing total deformation and collapsing of the block 40 in service and notwithstanding substantial side-to-side movements of the floating roof 20 with re estates such 'as petroleum products, and including a fioatingroof,

an improved sealing mechanism'for the annular space disposed between the upstanding. wall structure of the floating roof and the side wall of the tank.

'While there has been described what is at present consideredto be the preferred embodiment ofthe invention,

it"will be understood that various modifications may be madetherein, and it is intended to cover in the appended claimsall such modifications asfall within the true spirit and scope of the invention.

What is claimed is:

1 In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and.

including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining a substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing element arranged in said annular space and attached to said roof and movable therewith with respect to said tank side wall, said sealing element including a hollow tubular hermetically sealed casingformed of flexible non metallic sheet-like material that is impervious to the constituents of petroleum products and to water'and to air, said casing including annular inner and outer side walls arranged in opposing spacedapart relation and also annular bottomand top walls arranged in opposing spaced-apart relation, said casing inner side wall being disposed in direct contact and fixed I stituting a resilient cushion to urge said casing inner side.

wall into firm sealed relation with said wall structure and to urge said casing outer side wall intofirm sealed relation with said tan-k side wall during both vertical movements and sidewise movements of said roof with respectto said tank side wall, the material of said casing outer side wall also being highly wear-resistant to prevent undue scufling thereof in itssliding movements in direct contact with said tank side wall, the inner and outer surfaces of said body being attached to the respectively adjacent surfaces of said casing inner and outer side walls to prevent respective slippagestherebetween incident to vertical movements of said roof with respect I to said tank side wall, and means including a plurality of circumferentially spaced-apart members carried by said wall structure and attached to said sealing element for positively preventing said sealing element from riding-up said tank side wall and out of said annular space during downward movement of said roof with respect to said tank side Wall.

2. The sealing mechanism set forth in claim 1, wherein the material of said casing is formed essentially of copolymers of butadiene and acrylonitrile modified with polyvinyl chloride resin.

3. The sealing mechanism set forth in claim 1, wherein the material of said body is formed essentially of foamedsynthetic organic resin.

4. The sealing mechanism set forth in claim 1, wherein the material of said body is formed essentially of foamed polyurethane.

5. In a tank for storing liquids, such as petroleum prod ucts, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank andincluding upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side Wall and defining a substantially annular space therebetween; sealing mechanism for said annular space comprising a substanwith respect; to said tank sidewall, said sealing element including a hollow tubular hermetically sealed cas ing formed or flexible non metallic sheet-like material'that is impervious :to the constituents of petroleum productsvand to water and to air, said casing including annular inner and outer side wallsarranged in opposing spaced-apart relation and also annular bottom and top walls arranged in opposing spaced-apart relation, said casing inner side wall being disposed in direct contact and fixed sealed relation with said wall structure and said casing outer side Wall being disposed in" direct contact and sliding sealed relation with said tank side wall, said casing bottom wall being submerged in the stored liquid and said casing top wall being disposed well above the level of the stored liquid, said sealing element also including an annular ring of self-supporting resilient organic material of cellular structure enclosed by said casing and extending between said casing inner and outer side walls and constituting a resilient cushion to urge said casing inner side Wall into firm sealed relation with said wall structure and to urge said casing outer side wall into firm sealed relation with said tank side well during both vertical movements and sidewise movements of said roof with respect to said tank side wall, the material of said casing outer side wall also being highly wear-resistant to prevent undue scuffing thereof in its sliding movements in direct contact with said tank side wall, the inner and outer surfaces of said ring being attached to the respectively adjacent surfaces of said casing inner and outer side walls to prevent respective slippages therebetween incident to vertical movements of said roof with respect to said tank side wall, and means including a plurality of circumferentially spaced-apart members carried by said Wall structure and attached to said sealing element for positively preventing said sealing element from riding-up said tank side Wall and out of said annular space during downward movement of said roof with respect to said tank side Wall.

6. The sealing mechanism set forth in claim 5, wherein said ring has an annular series of circumferentially spaced-apart substantially upstanding passages formed therethrough to accommodate radial compression thereof between said wall structure and said tank side wall incident to sidewise movements of said roof toward said tank side wall.

7. The sealing mechanism set forth in claim 5, whereing top and bottom walls to accommodate movements therebetween incident to expansion and to contraction of segments of said ring incident to sidewise movements of said roof with respect to said tank side wall.

' 8. The sealing mechanism set forth in claim 5, wherein said ring occupies a major fraction of the volume of said casing and cooperates therewith to define a gas chamber in the residual minor fraction of the volume of said casing, whereby breathing of gas takes place between said ring and said gas chamber incident to expansion and to contraction of segments of said ring resulting from sidewisle movements of said roof With respect to said tank side wa 9. The sealing mechanism set forth in claim 8, wherein the major fraction of the volume of said casing oc cupied by said ring is about and said ring has a porosity of about 80%, whereby the total gas space in said casing is about of the total volume thereof.

10. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall,.and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side' wall and defining a substantiallyannular space therein said annular space and attached to said roof and movable therewith with respect to said tank side wall, said sealing element including a hollow tubular hermetically sealed casing formed of flexible non-metallic sheet-like material that is impervious to the constituents of petroleum products and to water and to air, said casing including annular inner and outer side walls arranged in opposing spaced-apart relation and also annular bottom and top walls arranged in opposing spaced-apart relation, said casing inner side wall being disposed in direct contact and fixed sealed relation with said wall structure and said casing outer side wall being disposed in direct contact and sliding sealed relation with said tank side wall, said casing bottom wall being submerged in the stored liquid and said casing top wall being disposed well above the level of the stored liquid, the material of said casing outer side wall also being highly wear-resistant to prevent undue scufiing thereof in its sliding movements in direct contact with said tank side wall, said sealing element also including an annular body of selfsupporting resilient material of cellular tructure enclosed by said casing and extending between said casing inner and outer side walls and constituting a resilient cushion to urge said casing inner side wall into fir-m sealed relation with said wall structure and to urge said casing outer side wall into firm sealed relation with said tank side wall during both vertical movements and sidewise movements of said roof with respect to said tank side wall,

the inner and outer surfaces of said body being attached to the respectively adjacent surfaces of said casing inner and outer side walls to prevent respective slippages therebetween incident to vertical movements of said roof with respect to said tank side wall, and means including a plurality of circumferentially spaced-apart stays carried by the upper portion of said wall structure and depending into said annular space and attached to said sealing element for positively preventing said sealing element from riding-up said tank side wall and out of said annular space during downward movement of said roof with respect to said tank side wall.

11. The sealing mechanism set forth in claim 10, wherein said sealing element occupies a major fraction of the volume of said annular space disposed above the level of the stored liquid and below the top of said wall structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,463,268 Hufi July 31, 1923 1,669,877 Maguire May 15, 1928 1,992,221 Kramer Feb. 26, 1935 2,092,877 Haupt et a1, Sept. 14, 1937 2,437,125 Plummer Mar. 2, 1948 2,523,292 Goldsby Sept. 26, 1950 2,914,212 Fine Nov. 24, 1959 2,968,420 Harris Jan. 17, 1961 

